Primary immune deficiencies (PIDs) are rare, life-threatening inherited defects in the immune system. The Primary Immune Deficiency Treatment Consortium (PIDTC) was established in 2009 and currently represents 5 Patient Advocacy Groups (PAGs) and, 33 centers in North America with broad expertise in genetics, molecular biology, immunology, hematopoietic cell transplantation (HCT), gene therapy (GT), enzyme replacement therapy (ERT) and medical management. The PAGs participate in PIDTC operations, subject recruitment, and dissemination of information resulting from our studies. The PIDTC is focused on three PIDs that can be cured with HCT, ERT or GT: Severe Combined Immunodeficiency (SCID), Wiskott - Aldrich syndrome (WAS) and chronic granulomatous disease (CGD). The Specific Aims of the PIDTC are: To characterize the long-term outcomes and late complications in children with SCID, WAS and CGD who undergo HCT, ERT and/or GT; To define the critical factors and biologic markers that predict the outcome of children with SCID, WAS and CGD following HCT, ERT and/or GT; To define the immunobiology of T and B cell reconstitution post HCT in long term survivors of SCID; To establish the minimal dose of chemotherapy necessary for sustained T and B cell reconstitution in children with SCID undergoing HCT regardless of donor source; To promote newborn screening for SCID in the US and other countries; To define biomarkers of autoimmunity in patients with WAS; To identify those patients with CGD who would most benefit from HCT; To train junior investigators in PID clinical research; and. To engage PAGs and share information between patients, parents, clinicians and scientists regarding the most up-to-date approaches to diagnosis and treatment of PIDs. Project 1 is a prospective study of typical and atypical SCID infants to identify early biomarkers and other disease- or HCT-related factors that affect engraftment, early immune reconstitution and survival. Project 2 is a cross-sectional/retrospective study of SCID, exploring factors that affect long term survival, immune reconstitution, late effects and quality of life (Qo). Project 3 addresses early and long-term outcomes following HCT in CGD, identifying which patients with CGD are most likely to benefit from HCT. Project 4 focuses on early and long-term outcomes following HCT in WAS to determine the degree of donor chimerism necessary for full disease correction and late effects including QoL. The Pilot Project will study biomarkers of autoimmunity in WAS patients undergoing HCT. These studies will resolve critical questions concerning HCT for these disorders and form the basis for future prospective clinical trials.